docs: def noisysphere(self, x, noise=2.10e-9, cond=1.0, noise_offset=0.10):
          """noise=10 does not work with default popsize, noise handling does not help """
          return self.elli(x, cond=cond) * (1 + noise * np.random.randn() / len(x)) + noise_offset * np.random.rand()